Highly Enantioselective Organocatalytic Sulfa-Michael Addition to α,β-Unsaturated Ketones

Abstract

A cinchona alkaloid-derived urea was found to be an efficient organocatalyst for catalyzing enantioselective conjugate addition between thiols and various alpha,beta-unsaturated ketones to provide optically active sulfides with high chemical yields (up to >99%) and enantiomeric excess (up to >99% ee). The reaction was performed with 0.1 mol % of catalyst in toluene at room temperature. A transition state model has been proposed to explain the stereochemical outcome of the reaction.

Recent applications of Cinchona alkaloids and their derivatives as catalysts in metal-free asymmetric synthesis

“…147 The Cinchona alkaloid urea 47e was identified as the most efficient catalyst, affording almost quantitative yields of the adducts 253 and >99% ee in some cases. According to the proposed transition-state model 254 (Fig.…”

Amine‐Urea‐Mediated Asymmetric Cycloadditions between Nitrile Oxides and o‐Hydroxystyrenes by Dual Activation

“…Recently, Houk et al. reported on computational studies of an asymmetric conjugate addition reaction catalyzed by a cinchona‐alkaloid‐derived amine‐urea . For the protonated 3 c (Figure , R 3 =Me), the anti ‐open and syn ‐open conformers were favored over other conformers .…”

Asymmetric Organocatalytic Reactions of α,β-Unsaturated Cyclic Ketones

“…It should be noted that in the (thio)urea derived catalyst depicted in entries 5 [71] and 8 [75] (Table 4) water plays a very different role. In fact on the former reaction, molecular sieves have to be added as water scavenger, while in the latter the addition of 4 Å MS has a negative effect on the enantioselectivity of the reaction.…”